How about we look at it like this:
Guy buying the tires = carrier
Joe's Tire Shop = broker
Goodyear = Manufacturer
The carrier agrees to take 10 Goodyear tires from Joe as long as they move freight from point A to point B. When the carrier completes this, Joe doesn't want to give the carrier any tires. Because Joe specifically said Goodyear tires, the carrier goes to Goodyear to get the tires. Goodyear already gave Joe 10 tires and now they have to give the carrier 10 more. Goodyear gives the carrier 10 tires because they are a reputable company and don't want bad publicity. Goodyear then charges Joe for the 10 tires they supplied to carrier. Goodyear also cuts off Joe's Tire Shop and now he is reduced to selling retreads.
The law works to protect the service provider because there are actual costs, not least of them labour charges. The people responsible for the freight are responsible to pay for it and if they pay the wrong entity, they pay again until they get it right. After that, they can deal with the other people who caused the grief to recoup their money. This type of thing happens and the Mercantile Act provides the best possible solution to it. I made it, I'm responsible to make sure the right person gets paid for moving it for me. If I choose to use a third party, I still maintain ultimate responsibility. If I choose to disregard that responsibility, why should anyone else pay? If the consignee winds up paying for it, don't you think they will ask for and get a credit from the manufacturer? Eventually, the unethical broker will get tapped. If manufacturers kept track of these crooks and passed it on to their associations we might not have this problem. Due diligence applies to everyone, equally.
My 2 cents.